Revert "Added entityx::make_ptr to mirror std::make_shared"

This reverts commit cc783cfc82ab99d90070193da71c4970bc08a96e.
Revert "Added std::forward in order to respect move semantics in some methods."

This reverts commit 9d5a03233f4b9495b8698ed8e4bad3d246cbbf13.